1. Field of the Invention
The present invention relates to a resilient shaft coupling having a radially inner rigid hub-like coupling part, an outer rigid coupling part, and a unitary, annular intermediate member that a is made of rubber or a similar material, and is operative to transmit torque between rigid parts. The intermediate member is secured to the inner part, for example by vulcanization. The outer periphery of the intermediate member is provided with pinion-like toothing that meshes, with provision for axial movement, with companion inner toothing of the outer part. The intermediate member comprises: a radially inner zone as a member of uniform torsional strength, i.e., it has an axial thickness that decreases radially outwardly; a short transition zone; and an outer zone which has the pinion-like toothing on its periphery, with the axial thickness of the outer zone corresponding approximately to the axial thickness of the inner zone on its inner periphery.
2. Description of the Prior Art
Resilient shaft couplings of this general type, also known as Bibby couplings, are primarily intended for use where the space available for installation is not accessible from the side. With the heretofore known resilient shaft couplings of this type, the intermediate member comprises a unitary annular rubber member. The torque which such a coupling can transmit is limited because, when a critical load is reached, the rubber toothing disengages from the inner toothing of the outer rigid coupling part. In operation, centrifugal force tends to partially oppose such disengagement by forcing the deformable rubber teeth outwardly into the inner toothing so that the clearances normally present are bridged.
To maximize the torque which a shaft coupling of this type can transmit, it has been conventional to make the resilient intermediate member of a relatively hard rubber. However, if a very high torsional resilience is required, the aforementioned approach is not practicable. The radial resilient length of the intermediate member cannot be increased because the external dimensions of the shaft coupling then also increase. When endeavors are made to achieve high torsional resilience by using a correspondingly soft rubber for a given performance and given dimensions, the risk of unreliable operation increases because the interval between the maximum transmissible torque and the average drive torque ceases to be sufficient.
To provide greater strength in the region of the toothing of the resilient intermediate member, a plain or profiled metal ring has been embedded in the rubber member near the toothing substantially over the entire axial length thereof. Consequently, when a plain ring is used the toothing can be strengthened radially; unfortunately, the advantageous effect of centrifugal force in operation of the coupling is eliminated. The use of a ring profiled to match the toothing leads to a substantially rigid toothing which in such a case basically consists of metal teeth having a thin covering of rubber. Also, because of their relatively substantial mass, the use of such metal rings, which extend substantially over the entire axial length of the rubber member, may produce additional stressing of the coupling in drives where vibration is likely to occur. Furthermore, wide rings are also relatively expensive.
An object of the present invention therefore is to further develop and improve a resilient shaft coupling of this kind in order to obviate the drawbacks previously set forth; i.e., the object of the invention is to provide a resilient shaft coupling which has relatively high torsional resilience yet can reliably transmit higher torques than can known shaft couplings of substantially the same size.